NC0003573_Correspondence_20201220

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GEOServioes, LLC, Geotechnical and Materials Engineers
Chemours Fayetteville Works — Outfall 003 Sediment Removal Workplan
1 Project Obiectives
Based on the current sediment loading at Outfall 003 sediment buildup is required to be removed prior
to reaching the intake structures for the wastewater treatment plant and minimize any potential
damage to the intake and treatment systems. The objective is to remove sediment that is not in
solution from the channel. This maintenance will minimize the amount of sediment migrating on the
channel bed and maintain the original design elevations. Figure 1 displays the project area and Figure 2
displays the current migration of the sediment.
WWTP Intake and Dam
Figure 1 — Project Area
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Figure 2—Sediment Migration
GEOServices, LLC 1 5559 North Lee Highway, Cleveland, TN 379311 Phone [phone] Fax [phone] www.geoserviceslic.com

Sediment Removal Workplan
Outfall 003 — Fayetteville, North Carolina
2 Proposed Corrective Action Plan
GEOServices Project No. 45-20400A
December 16, 2020
After field review of the sediment loading in the channel at Outfall 003, corrective activities are required
to protect the downstream infrastructure. GEOServices will implement long-term maintenance and
near -term corrective action. During the corrective action activities, some phases likely will be performed
simultaneously with others.
1. Phase I (Mechanical Removal of Sediment): Temporary access roadways are in the process of
being constructed on the project site to allow for sediment removal and to facilitate the
transportation of the sediment material to a stockpile location area. After completion of the
temporary access roads, a work area will be developed adjacent to the channel. Figure 3 below
documents the initial haul road to be utilized for the removal.
Figure 3 — Access Road
After installing temporary access adjacent to the channel, a long reach excavator will be utilized
to mechanically remove the excess sediment, see Figure 4 below. The sediment will be hauled
to a stockpile/dewatering area adjacent to the wastewater treatment plant outside of the 100-
year floodplain, see figure 5.
Figure 4 —Sediment Excavation Area
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Sediment Removal Workplan
Outfall 003 — Fayetteville, North Carolina
Figure 5 — Stockpile Area
GEOServices Project No. 45-20400A
December 16, 2020
The stockpile area will be graded to drain towards the creek to allow the water to drain to the
outfall channel. The water in the outfall channel will be captured by the wastewater treatment
plant intakes and treated prior to discharging downstream of the dam, through Outfall 003.
The stockpile area will be surrounded by a combination of silt fence and haybales. The floor of
the stockpile area will be lined with Visqueen plastic liner and graded to drain on the creek side.
Based on the required timely response and the uncertainty of the volume of sediment in the
channel, this activity may be required multiple times to capture the sediment that is accessible.
As an alternative for the immediate action Chemours is procuring materials and equipment to
address multiple clean outs prior to Phase II being permitted and constructed. The alternative
method includes the use of a hydraulic cutting head (See Figure 6) to remove the sediment and
transport directly to Geotube° (See Figure 7) for dewatering, where water will drain to the
upstream side of the dam and allow for treatment at the WWTP.
Figure 6 — Hydraulic Cutting Head
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Sediment Removal Workplan GEOServices Project No. 45-20400A
Outfall 003 — Fayetteville, North Carolina December 16, 2020
Figure 7 — Geotube° Dewatering System
2. Phase II (Long -Term Maintenance): Based on limited reach of the excavator in the channel, we
anticipate multiple maintenance activities will be required. To allow for future maintenance
activities and to enhance our ability to extend the reach of the excavator, we will be proposing
to build an access platform within the channel and installing a rock check dam to minimize the
amount of sediment that reaches the intakes. We anticipate the check dam to be
approximately 4 feet high and 24 feet in length, but the final determination will be based on the
information gathered during Phase I. Phase 11, the Long -Term Maintenance plan, will be
designed to minimize the amount of maintenance and sediment loss, but is the longer -term
solution although Phase I will dictate the final needs and schedule of Phase 11.
At this time, Phase I is the requested action and the permit and construction requirements will be
developed in the future for Phase II action.
3. Phase 1 Mechanical Sediment Removal
Standard excavation equipment will be used to remove the materials from the channel. A track -
mounted excavator will be used to remove the sediment and loaded into trucks for transport back to a
stockpile area adjacent to the wastewater treatment plant for proper storage until final disposal can be
determined.
Sediment Removal Activities
• Mobilizing equipment and personnel
• Construct temporary access to the area adjacent to the channel
• Completing minor improvements to the existing surface adjacent to the wastewater treatment
plant for a stockpile and dewatering area utilizing erosion and sediment control best
management practices
• Install silt curtains in the channel in the vicinity of the wastewater treatment plant intake
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Sediment Removal Workplan
Outfall 003 — Fayetteville, North Carolina
GEOServices Project No. 45-20400A
December 16, 2020
Begin mechanical excavation of the sediment
Characterization of sediment for disposal per the Soil and Materials Waste Management Plan.
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